Percutaneous registration apparatus and method for use in computer-assisted surgical navigation

ABSTRACT

An apparatus and procedures for percutaneous placement of surgical implants and instruments such as, for example, screws, rods, wires and plates into various body parts using image guided surgery. The invention includes an apparatus for use with a surgical navigation system, an attaching device rigidly connected to a body part, such as the spinous process of a vertebrae, with an identification superstructure rigidly but removably connected to the attaching device. This identification superstructure, for example, is a reference arc and fiducial array which accomplishes the function of identifying the location of the superstructure, and, therefore, the body part to which it is fixed, during imaging by CAT scan or MRI, and later during medical procedures.

This application is a reissue of U.S. Pat. No. 6,226,548 issued on May1, 2001 and also claims benefit under 35 U.S.C. §120 as a reissuecontinuation of U.S. patent application Ser. No. 13/036,939, filed onFeb. 28, 2011, now U.S. Pat. No. Re. 44,305, issued on Jun. 18, 2013;which also claims benefit under 35 U.S.C. §120 as a continuation of U.S.patent application Ser. No. 11/451,594, filed on Jun. 12, 2006, now U.S.Pat. No. Re. 42,194; which also claims benefit under 35 U.S.C. §120 as acontinuation of U.S. patent application Ser. No. 10/423,332 filed onApr. 24, 2003, now U.S. Pat. No. Re. 39,133; which is also a reissue ofU.S. Pat. No. 6,226,548 issued on May 1, 2001; which claims rights under35 U.S.C. §119 of provisional application No. 60/059,915, filed on Sep.24, 1997.

U.S. patent application Ser. No. 13/036,939, filed on Feb. 28, 2011, nowU.S. Pat. No. Re. 44,305, issued on Jun. 18, 2013; also claims benefitunder 35 U.S.C. §120 as a continuation of U.S. patent application Ser.No. 11/451,595, filed on Jun. 12, 2006, now U.S. Pat. No. Re. 42,226;which also claims benefit under 35 U.S.C. §120 as a continuation of U.S.patent application Ser. No. 10/423,332 filed on Apr. 24, 2003; which isa reissue of U.S. Pat. No. 6,226,548 issued on May 1, 2001; which claimsrights under 35 U.S.C. §119 of provisional application No. 60/059,915,filed on Sep. 24, 1997.

The present invention claims rights under 35 U.S.C. §119 on provisionalapplication No. 60/059,915, filed on Sep. 24, 1997, and entitled“Percutaneous Registration Apparatus and Method for Use inComputer-Assisted Surgical Navigation.”

FIELD OF THE INVENTION

The present invention relates generally to guiding, directing, ornavigating instruments or implants in a body percutaneously, inconjunction with systems that use and generate images during medical andsurgical procedures, which images assist in executing the procedures andindicate the relative position of various body parts, surgical implants,and instruments. In particular the invention relates to apparatus andminimally invasive procedures for navigating instruments and providingsurgical implants percutaneously in the spine, for example, to stabilizethe spine, correct deformity, or enhance fusion in conjunction with asurgical navigation system for generating images during medical andsurgical procedures.

BACKGROUND OF THE INVENTION

Typically, spinal surgical procedures used, for example, to providestabilization, fusion, or to correct deformities, require largeincisions and substantial exposure of the spinal areas to permit theplacement of surgical implants such as, for example, various forms ofscrews or hooks linked by rods, wires, or plates into portions of thespine. This standard procedure is invasive and can result in trauma,blood loss, and post operative pain. Alternatively, fluoroscopes havebeen used to assist in placing screws beneath the skin. In thisalternative procedure at least four incisions must be made in thepatient's back for inserting rods or wires through previously insertedscrews. However, this technique can be difficult in that fluoroscopesonly provide two-dimensional images and require the surgeon to rotatethe fluoroscope frequently in order to get a mental image of the anatomyin three dimensions. Fluoroscopes also generate radiation to which thepatient and surgical staff may become over exposed over time.Additionally, the subcutaneous implants required for this procedure mayirritate the patient. A lever arm effect can also occur with the screwsthat are not connected by the rods or wires at the spine. Fluoroscopicscrew placement techniques have traditionally used rods or plates thatare subcutaneous to connect screws from vertebra to vertebra. This isdue in part to the fact that there is no fluoroscopic technique that hasbeen designed which can always adequately place rods or plates at thesubmuscular region (or adjacent to the vertebrae). These subcutaneousrods or plates may not be well tolerated by the patient. They also maynot provide the optimal mechanical support to the spine because themoment arm of the construct can be increased, thereby translating higherloads and stresses through the construct.

A number of different types of surgical navigation systems have beendescribed that include indications of the positions of medicalinstruments and patient anatomy used in medical or surgical procedures.For example, U.S. Pat. No. 5,383,454 to Bucholz; PCT Application No.PCT/US94/04530 (Publication No. WO 94/24933) to Bucholz; and PCTApplication No. PCT/US95/12894 (Publication No. WO 96/11624) to Bucholzet al., the entire disclosures of which are incorporated herein byreference, disclose systems for use during a medical or surgicalprocedure using scans generated by a scanner prior to the procedure.Surgical navigation systems typically include tracking means such as,for example, an LED array on the body part, LED emitters on the medicalinstruments, a digitizer to track the positions of the body part and theinstruments, and a display for the position of an instrument used in amedical procedure relative to an image of a body part.

Bucholz et al. WO 96/11624 is of particular interest, in that itidentifies special issues associated with surgical navigation in thespine, where there are multiple vertebral bodies that can move withrespect to each other. Bucholz et al. describes a procedure foroperating on the spine during an open process where, after imaging, thespinous process reference points may move with respect to each other. Italso discloses a procedure for modifying and repositioning the imagedata set to match the actual position of the anatomical elements. Whenthere is an opportunity for anatomical movement, such movement degradesthe fidelity of the pre-procedural images in depicting theintra-procedural anatomy. Therefore, additional innovations aredesirable to bring image guidance to the parts of the body experiencinganatomical movement.

Furthermore, spinal surgical procedures are typically highly invasive.There is, thus, a need for more minimally invasive techniques forperforming these spinal procedures, such as biopsy, spinal fixation,endoscopy, spinal implant insertion, fusion, and insertion of drugdelivery systems, by reducing incision size and amount. One such way isto use surgical navigation equipment to perform procedurespercutaneously, that is beneath the skin. To do so by means of surgicalnavigation also requires apparatus that can indicate the position of thespinal elements, such as, for example the vertebrae, involved in theprocedure relative to the instruments and implants being insertedbeneath the patient's skin and into the patient's spine. Additionally,because the spinal elements naturally move relative to each other, theuser requires the ability to reorient these spinal elements to alignwith earlier scanned images stored in the surgical navigation systemcomputer, to assure the correct location of those elements relative tothe instruments and implants being applied or inserted percutaneously.

In light of the foregoing, there is a need in the art for apparatus andminimally invasive procedures for percutaneous placement of surgicalimplants and instruments in the spine, reducing the size and amount ofincisions and utilizing surgical navigation techniques.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to apparatus andprocedures for percutaneous placement of surgical implants andinstruments such as, for example, screws, rods, wires and plates intovarious body parts using image guided surgery. More specifically, oneobject of the present invention is directed to apparatus and proceduresfor the percutaneous placement of surgical implants and instruments intovarious elements of the spine using image guided surgery.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, theinvention includes an apparatus for use with a surgical navigationsystem and comprises an attaching device rigidly connected to a bodypart, such as the spinous process of a vertebrae, with an identificationsuperstructure rigidly but removably connected to the attaching device.This identification superstructure is a reference arc and fiducialarray, which accomplishes the function of identifying the location ofthe superstructure, and, therefore, the body part to which it is fixed,during imaging by CAT scan or MRI, and later during medical procedures.

In one aspect, the attaching device is a clamp with jaws and sharp teethfor biting into the spinous process.

In another aspect, the fixture is a screw, having a head, wherein thescrew is implanted into the spinous process and a relatively rigid wireis attached to the head of the screw and also implanted into the spinousprocess at an angle to the axis of the screw to prevent the screw fromrotating in either direction.

In another aspect, the superstructure includes a central post, and afiducial array and a reference arc rigidly but removably attached to thecentral post. The fiducial array is composed of image-compatiblematerials, and includes fiducials for providing a reference point,indicating the position of the array, which are rigidly attached to thefiducial array, composed of, for example titanium or aluminum spheres.The reference arc includes emitters, such as, for example Light EmittingDiodes (“LEDs”), passive reflective spheres, or other tracking meanssuch as acoustic, magnetic, electromagnetic, radiologic, or micropulsedradar, for indicating the location of the reference arc and, thus, thebody part it is attached to, during medical procedures.

In addition, the invention further comprises a method for monitoring thelocation of an instrument, surgical implants and the various portions ofthe body, for example, vertebrae, to be operated on in a surgicalnavigation system comprising the steps of: attaching a fixture to thespinous process; attaching a superstructure including a fiducial arraywith fiducials and a reference arc to the fixture; scanning the patientusing CT, MRI or some other three-dimensional method, with fiducialarray rigidly fixed to patient to identify it on the scanned image; andthereafter, in an operating room, using image-guided technology,touching an image-guided surgical pointer or other instrument to one ormore of the fiducials on the fiducial array to register the location ofthe spinal element fixed to the array and emitting an audio, visual,radiologic, magnetic or other detectable signal from the reference arcto an instrument such as, for example, a digitizer or otherposition-sensing unit, to indicate changes in position of the spinalelement during a surgical procedure, and performing a surgical ormedical procedure percutaneously on the patient using instruments andimplants locatable relative to spinal elements in a known position inthe surgical navigation system.

In another aspect, the method includes inserting screws or rigid wiresin spinal elements in the area involved in the anticipated surgicalprocedure before scanning the patient, and after scanning the patientand bringing the patient to the operating area, touching an image-guidedor tracked surgical pointer to these screws and wires attached to thevertebrae to positively register their location in the surgicalnavigation computer, and manipulating either the patient's spine or theimage to align the actual position of the spinal elements with thescanned image.

In another aspect, the method includes percutaneously implanting screwsinto spinal elements, which screws are located using image guidedsurgical navigation techniques, and further manipulating the orientationof the screw heads percutaneously using a head-positioning probecontaining an emitter, that can communicate to the surgical navigationcomputer the orientation of the screw heads and position them, by use ofa specially designed head-positioning tool with an end portion thatmates with the heads of the screws and can rotate those screw heads toreceive a rod, wire, plate, or other connecting implant. If a rod isbeing inserted into the screw heads for example, the method furtherincludes tracking the location and position of the rod, percutaneouslyusing a rod inserter having one or more emitters communicating thelocation and orientation of the rod to the surgical navigation computer.

The objects of the invention are to provide a user, such as a surgeon,with the system and method to track an instrument and surgical implantsused in conjunction with a surgical navigation system in such a mannerto operate percutaneously on a patient's body parts, such as spinalvertebrae which can move relative to each other.

It is a further object of this invention to provide a system and methodto simply and yet positively indicate to the user a change in positionof body parts, such as spinal vertebrae segments, from that identifiedin a stored image scan, such as from an MRI or CAT scan, and provide amethod to realign those body parts to correspond with a previouslystored image or the image to correspond with the actual current positionof the body parts.

It is a further object of this invention to provide a system or methodfor allowing a fiducial array or reference arc that is removable from alocation rigidly fixed to a body part and replaceable back in thatprecise location.

It is another object of this invention to provide a system and methodfor positively generating a display of instruments and surgicalimplants, such as, for example screws and rods, placed percutaneously ina patient using image-guided surgical methods and techniques.

It is another object of this invention for a percutaneous referencearray and fiducial array, as described in this appplication, to be usedto register and track the position of the vertebrae for the purposes oftargeting a radiation dose to a diseased portion of said vertebrae usinga traditional radiosurgical technique.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in thisdescription.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one embodiment of the inventionand together with the description, serve to explain the principles ofthe invention.

FIG. 1 is a schematic diagram of one preferred embodiment of asuperstructure for use in the current invention, including a referencearc, center post and fiducial array and rigid Kirschner wires (“Kwires”) and screws placed in the spine for use with a surgicalnavigation system for percutaneous spinal surgical procedures.

FIG. 1A is an enlarged view of the superstructure depicted in FIG. 1engaging a vertebra by a clamp and also K wires implanted in adjacentvertebrae in the superior and inferior positions of the spinous process.

FIG. 2 is a diagram of the preferred embodiment of a clamp fixture forrigid connection to the spinous process of a single vertebrae with anH-shaped fiducial array attached to a center post rigidly attached tothe clamp and a mating connector at the tip of the post for mating witha reference array, and a reference array for use in the currentinvention.

FIG. 2A is a side view of FIG. 2 FIG. 2B is another side view of FIG. 2.

FIG. 2C is a top view of FIG. 2.

FIG. 2D is an exploded view of FIG. 2 without the reference arc.

FIG. 2E is an exploded view of the interface of the center post andclamp of FIG. 2.

FIG. 3 is a diagram of a W-Shaped fiducial array mounted to a centralpost with generally spherical fiducials attached to the array, formounting to a single vertebrae.

FIG. 3A is a side view of FIG. 3.

FIG. 3B is another side view of FIG. 3.

FIG. 3C is a top view of FIG. 3.

FIG. 4 is a diagram of a reference arc and fiducial attached to a centerpost for use in the current invention in mounting to a single vertebrae.

FIG. 4A is a side view of FIG. 4.

FIG. 4B is a back view of FIG. 4.

FIG. 4C is a top view of FIG. 4.

FIG. 4D is an expanded view of FIG. 4.

FIG. 4E is an expanded side view of FIG. 4.

FIG. 4F is an expanded view of the array foot and shoe of FIG. 4E.

FIG. 5 is a diagram of an alternative embodiment of a fixture for use inthe current invention using a cannulated screw for insertion into avertebrae, with Kirschner wire mounted on a central post and includingan alternate embodiment of a fiduciary array and reference arc combinedon a single structure.

FIG. 6 is a side view of the screw and Kirschner wire fixture of FIG. 5implanted in a spinous process of a vertebrae.

FIG. 7 is a diagram of a screw-head positioning probe and multiaxialscrew for insertion into a single vertebrae.

FIG. 7A is a diagram of the screw of FIG. 7.

FIG. 8 is a diagram of a head positioning probe, multiaxial screw andspinal segment.

FIG. 9 is a diagram of a rod inserter with an LED.

FIG. 10 is a diagram of an alternative embodiment of the inventiondepicting a cannulated tube and attachment for holding a reference arc.

FIG. 11 is a diagram of the cannulated tube of FIG. 10 with a referencearc and screw for attachment to a spinal process.

FIG. 12 is a posterior view of spinal segment and implanted screwsbefore alignment.

FIG. 13 is a posterior view of spinal segment and implanted screws afteralignment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the present preferred embodimentof the invention, an example of which is illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. Thefollowing example is intended to be purely exemplary of the invention.

As generally described in PCT/US95/12894, the entire disclosure of whichis incorporated herein by reference, a typical surgical navigationsystem is shown in FIG. 1 adopted to be used in the present invention. Acomputer assisted image-guided surgery system, indicated generally at10, generates an image for display on a monitor 106 representing theposition of one or more body elements, such as spinal elements fixedlyheld in a stabilizing frame or device such as a spinal surgery frame 125commonly used for spinal surgery. A reference arc 120 bearing trackingmeans or emitters, such as for example LED emitters 122, is mounted tothe spinous process by a central post 150. The structures 20 and K wires260 of FIG. 1 are depicted in more detail in FIG. 1A. The image 105 isgenerated from an image data set, usually generated preoperatively by aCAT scanner or by MRI for example, which image 105 has reference pointsfor at least one body element, such as a spinal element or vertebrae.The reference points of the particular body element have a fixed spatialrelation to the particular body element.

The system includes an apparatus such as a digitizer or other PositionSensing Unit (PSU), such as for example sensor array 110 on support 112for identifying, during the procedure, the relative position of each ofthe reference points to be displayed by tracking the position ofemitters 122 on arc 120. The system also includes a processor 114 suchas a PC or other suitable workstation processor associated withcontroller 108 for modifying the image data set according to theidentified relative position of each of the reference points during theprocedure, as identified by digitizer 110. The processor 114 can then,for example, generate an image data set representing the position of thebody elements during the procedure for display on monitor 106. Asurgical instrument 130, such as a probe or drill or other tool, may beincluded in the system, which is positioned relative to a body part andsimilarly tracked by sensor array 110.

In summary, the general operation of a surgical navigating system iswell known in the art and need not further be described here.

In accordance with the preferred embodiment of the present invention,with further reference to FIGS. 1 through 6, a registration device 20 isrigidly fixed to a spinal element by, for example, a device such as abone clamp 30 depicted in FIG. 2. Alternatively, a screw retentiondevice 40, such as the cannulated screw 42 depicted in FIG. 5, anddescribed in more detail below, can be used.

With reference now to FIG. 2, bone clamp 30 is fixedly attached to thespinous process. The clamp 30 includes at so least two blades (or jaws)32 with tips or teeth 34, which are preferably sharp, for drivingtogether and penetrating soft tissue or more dense bone for rigidfixation to the spinous process. The teeth 34 are also preferably sizedto accommodate the bulb shape of the spinous process. The drivingmechanism 40 is, for example, a screw driven into a sleeve 41 and isalso preferably located such that it will be accessible in apercutaneous manner. Attached to the clamp 30 is a superstructure 20.The superstructure 20 includes a central post 150 which is relocatable,that is, it fixes to the clamp 30 in a rigid fashion, for example, asdepicted in FIGS. 2D and 2E, by being inserted into a V-shaped wedge 44orienting the post 150 front to back and providing a mating hole 48along the wedge 44 for insertion of post 150 in a single orientation andalso providing fasteners such as screw 43 for tightning to lock the post150 in place. The post 150 can be removed and reapplied by loosening andtightening screw 43, such that the original geometry and orientation ismaintained. The central post 150 has at its apex a connector 60 withunique geometrical configuration, such as, for example, a starburst,onto which a spinal reference arc 120 of the superstructure 20 attaches.Any such standard reference arc 120 can be used, such as depicted inFIGS. 1A, 4, and 11, preferably including emitters 122, such as forexample LEDs or reflective spheres for providing a positive indicationof movement to the surgical navigation system during a procedure.

Also rigidly attached to the central post 150, as part of thesuperstructure 20 preferably at a location closer to the skin, orpossibly collocated with or also performing the function of thereference arc 120, is a fiducial array 170, which can be of variousdifferent shapes, such as, for example the H-shaped frame 170 depictedin FIG. 2, the W-shaped frame 170′ as depicted in FIG. 3, the U-shapedframe 170″ as depicted in FIG. 4 or the X-shaped frame 120′, 170″′depicted in FIG. 5 (depicting a structure that is both a fiducial arrayand a reference arc). As depicted in FIGS. 2 and 3, this array caninclude fiducial points 29 or spheres 17, rigidly attached to fiducialarray 170, 170′ and is, for example, as depicted in FIG. 3,substantially in the shape of spheres 17 and of a material detectable bythe CAT scan or MRI, preferably titanium or aluminum. This fiducialarray such as 170 indicates to the surgical navigation system thelocation of the bone structure to which the clamp 30 and central post150 are attached by touching a pointed surgical tracker to fiducialpoints 29 or a cup-shaped probe to fiducial spheres 17, therebyindicating the center of the fiducial to the surgical navigationcontroller 114. The array 170 and central post 150 are also attached tothe clamp 30, as described above, in such a way that they can be removedand replaced in the same geometric orientation and location, forexample, by means of a uniquely shaped interface, for example, atriangle, or a single unique shape or a combination of unique angles orpins with the clamp 30 such that the post 150 can only be reinserted thesame way it was removed.

Additionally, the fiducial array 170, can be located at various heightson the post 150 to accomodate variations in patient tissue depth andsize, preferably as close to the patient's body as possible, and thenfixed at that specific height by the use of pins or indents matched toholes 19 (shown in FIG. 2) in the central post 150 or by placing therods 39 of H-shaped array 170 in different holes 31. The fiducial array170 also has, for example, divots 29 (shown in FIG. 2) shaped tointerface with an instrument such as a surgical pointer 130 which cantouch that divot 29 to register the location of the divot 29 and, thus,the location of the fiducial array 170 and likewise the spinal elementin the surgical navigation system. Multiple divots can be registered tofurther increase accuracy of the registration system. In one preferredembodiment of the array, the fiducials 17 or 29 can be mounted in amanner such that they can be adjusted, for example by mounting them on arotatable or collapsible arm 66 (as depicted in FIG. 3) that pivots andfolds together, to get the maximum distance between fiducials while notdramatically increasing the field of view required at the time ofscanning.

Alternatively, rather than using clamp 30, a screw 42 and rigid wire 45attachment, as depicted in FIGS. 5 and 6, may be used to rigidly attachthe central post of the superstructure 20 to a body element, such as,for example, a vertebrae. As depicted in FIG. 6, screw 42 is screwedinto the spinal process of spinal element 100. A rigid wire 45, post, orother sufficiently rigid fastener such as for example a Kirschner wire(K-wire), is inserted through the cannulation in the center of post 150and the screw 42 or is otherwise fixed to the screw 42, and exits thetip of the screw 42 at some angle, and is also implanted into the spinalelement 100 to prevent the screw 42 from rotating in either direction.

Another embodiment for preventing the superstructure 20 from rotating asdepicted in FIGS. 10 and 11 includes the insertion of a screw 85 througha cannulated tube 86 which has teeth 89 in the end (or V-shaped end)that would bite into the tip of the spinous process, preventingrotation.

Having described the preferred embodiment of this apparatus of thepresent system, the method of using this apparatus to practice theinvention of registering a single vertebrae will now be discussed. Theoperation of a surgical navigating system is generally well known and isdescribed in PCT/US95/12894. In the preferred method of operation, clamp30 of FIG. 2 or screw 42 and K-Wire 45 of FIG. 5 are implantedpercutaneously through a small incision in the skin and rigidly attachedto the spinal process. This attachment occurs with the clamp 30, bydriving the blades 32 of the clamp 30 together to hold the spinousprocess rigidly. The central post 150 is then rigidly fixed to the clamp30 or screw 42 and the fiducial array 170 is rigidly fixed to thecentral post 150. The patient is then scanned and imaged with a CAT scanor MRI with a field of view sufficiently large to display the spinalanatomy and the clamp 30 or screw 42 and the fiducial array 170. Thisscan is loaded into the surgical navigation system processor 104.

After scanning the patient, the array 120 and post 150 can be removedfrom the patient, while leaving in place the rigidly connected clamp 30or screw 42. For example, as depicted in FIGS. 4D and 4E, a foot 55located below array 170″ engages with shoe 56 and rigidly connected byscrews 57 and 58. Before the surgical procedure, the post 150, array 120and other remaining portions of the superstructure 20, once removed, maybe sterilized. The patient is then moved to the operating room orsimilar facility from, for example, the scanning room.

Once in the operating room, the patient may be positioned in anapparatus, such as, for example, a spinal surgery frame 125 to help keepthe spinal elements in a particular position and relatively motionless.The superstructure 20 is then replaced on the clamp 30 or screw 42 in aprecise manner to the same relative position to the spinal elements asit was in the earlier CAT scan or MRI imaging. The reference arc 120 isfixed to the starburst or other interface connector 60 on the centralpost 150 which is fixed to the clamp 30 or screw 42. The operator, forexample a surgeon, then touches an instrument with a tracking emittersuch as a surgical pointer 130 with emitters 195 to the divots 29 on thefiducial array 170 to register the location of the array 170 and, thus,because the spinal process is fixed to the fiducial array 170, thelocation of the spinal element is also registered in the surgicalnavigation system.

Once the superstructure 20 is placed back on the patient, any instrument130 fitted with tracking emitters thereon such as, for example, a drillor screw driver, can be tracked in space relative to the spine in thesurgical navigation system without further surgical exposure of thespine. The position of the instrument 130 is determined by the userstepping on a foot pedal 116 to begin tracking the emitter array 190.The emitters 195 generate infrared signals to be picked up by cameradigitizer array 110 and triangulated to determine the position of theinstrument 130. Additionally, other methods may be employed to trackreference arcs, pointer probes, and other tracked instruments, such aswith reflective spheres, or sound or magnetic emitters, instead ofLED's. For example, reflective spheres can reflect infrared light thatis emitted from the camera array 110 back to the camera array 110. Therelative position of the body part, such as the spinal process isdetermined in a similar manner, through the use of similar emitters 122mounted on the reference frame 120 in mechanical communication with thespinal segment. As is well known in this art and described generally inPCT/US95/12894, based upon the relative position of the spinal segmentand the instrument 130 (such as by touching a known reference point) thecomputer would illustrate a preoperative scan—such as the proper CATscan slice—on the screen of monitor 106 which would indicate theposition of the tool 130 and the spinal segment for the area of thespine involved in the medical procedure.

For better access by the operator of various areas near the central post150, the fiducial array 170 can be removed from the central post 150,by, for example, loosening screw 42 and sliding the array 170 off post150, leaving the reference arc 120 in place or replacing it afterremoval of array 170. By leaving the reference arc 120 in place, theregistration of the location of the spinal process is maintained.Additionally, the central post 150, reference arc 120, and fiducialarray 170 can be removed after the spinal element has been registeredleaving only the clamp 30 or screw 42 in place. The entire surgicalfield can then be sterilized and a sterile post 150 and reference arc170 fixed to the clamp 30 or screw 42 with the registration maintained.

This surgical navigation system, with spinal element registrationmaintained, can then be used, for example, to place necessary anddesired screws, rods, hooks, plates, wires, and other surgicalinstruments and implants percutaneously, using image-guided technology.Once the location of the spinal element 100 involved in the procedure isregistered, by the process described above, in relation to the imagedata set and image 105 projected on monitor 106, other instruments 130and surgical implants can be placed under the patient's skin atlocations indicated by the instrument 130 relative to the spinal element100.

Additionally, the location of other spinal elements, relative to thespinal element 100 containing the fiducial array 170, can be registeredin the surgical navigation system by, for example, inserting additionalscrews 250, rigid wires 260, or other rigid implants or imageabledevices into the spinal segment.

For example, as depicted in FIG. 1, and in more detail FIG. 1A,additional screws 250 or rigid and pointed wires 260 are placed in thevertebrae adjacent to the vertebrae containing the clamp 30 and post 150prior to scanning. On the image 105 provided by monitor 106, the surgeoncan see the clamp 30 or screw 42 and fiducial array 170 and also theadditional screws 250, wires 260 or other imageable devices. When screws250 or other devices are used, these screws 250 (as depicted in FIG. 7)may contain a divot 256 or other specially shaped interface on the head255 so that a pointer probe 130 can be used to point to the head 255 ofthe screw 250 (or wire) and indicate the orientation of the screw 250 orwire 260 to the surgical navigation system by communicating to thecontroller 114 or by emission from LEDs 195 on probe 130 to digitizer110. The image of these additional screws 250 also appear in the scan.Once the patient is then moved to the operating facility, rather thanthe scanning area, the image of the screw 250 can be compared to theactual position of the screw 250 as indicated by the pointer probe 130that is touched to the head 255 of the screw 250 or wire 260. Ifnecessary, the operator can manipulate the position of the patient tomove the spinal element and thus the location of the screw 250 or wire260 to realign the spinal elements with the earlier image of the spine.Alternatively, the operator can manipulate the image to correspond tothe current position of the spinal segments.

For additional positioning information, the operator can placeadditional rigid wires 260 or screws 250 into the vertebrae, forexample, located at the superior (toward the patient's head) andinferior (towards the patient's feet) ends of the spinal process to moreaccurately position those vertebrae relative to the other vertebrae andthe image data. Additionally, the wires 260 and screws 250 implanted toprovide positioning information can also be equipped with emitters, suchas, for example, LEDs, to provide additional information to the surgicalnavigation system on the location of the wire 260 or screw 250, and thusthe vertebra to which they are affixed.

Alternatively, the patient can be placed in a position stabilizingdevice, such as a spinal surgery frame 125 or board, before a scan istaken, and then moved to the operating facility for the procedure,maintaining the spine segments in the same position from the time ofscanning until the time of surgery. Alternatively, a fluoroscope can beused to reposition the spinal segments relative to the earlier imagefrom the scan. An ultrasound probe can be used to take real-time imagesof the spinal segment which can be portrayed by monitor 106 overlayed orsuperimposed on image 105. Then the operator can manually manipulate thespinal elements and take additional images of these elements with thefluoroscope to, in an iterative fashion, align the spinal elements withthe previously scanned image 105.

Alternatively, a clamp 30 or screw 42 and superstructure 20 can berigidly fixed to each vertebra involved in the surgical or medicalprocedure to register the position of each vertebra as explainedpreviously for a single vertebra:

After the spinal elements are registered in the spine, various medicaland surgical procedures can be performed on that patient. For example,spinal implants, endoscopes, or biopsy probes can be passed into thespine and procedures such as, for example, spinal fusion, manipulation,or disc removal can be performed percutaneously and facilitated by thesurgical navigation image-guiding system. Additionally, a radiation dosecan be targeted to a specific region of the vertebrae.

One such procedure facilitated by the apparatus and methods describedabove is the percutaneous insertion of screws and rods, fixed todifferent vertebra in a spine to stabilize them. Once screws, forexample multiaxial screws 250, (as depicted in FIG. 12, beforemanipulation) are implanted through small incisions they can bemanipulated by a head-positioning probe 280. The final position ofscrews 250 and heads 255 are depicted in FIG. 13. This probe 280, asdepicted in FIG. 7, includes a head 285 that mates in a geometricallyunique fashion with the head 255 of the screw 250. An emitter, such asfor example an LED array 380 on the probe 280, indicates the locationand orientation of the screw head 255 to the computer 114 of thesurgical navigation system by providing an optical signal received bydigitizer 110. The screw head 255 can then be rotatably manipulatedunder the patient's skin by the head positioning probe 280 to beproperly oriented for the receipt of a rod 360 inserted through therotating head 255. The operator can then plan a path from the head 255of each screw 250 to the other screws 250 to be connected. Then, withreference now to FIG. 9, an optically tracked rod inserter 245 alsoequipped with emitters, such as, for example LEDs 247, can be placedthrough another small incision to mate with and guide a rod 360 throughthe holes or slots in the screw heads 245, through and beneath varioustissues of the patient, with the rod inserter 245, and, therefore, therod 360, fixed to the inserter 245, being tracked in the surgicalnavigation system. The operator can also use the computer 114 todetermine the required bending angles of the rod 360. For greatervisualization, the geometry of the screws 250 could be loaded into thecomputer 114 and when the position and orientation of the head 255 isgiven to the computer 114 via the probe 280, the computer 114 couldplace this geometry onto the image data and three-dimensional model. Therod 360 geometry could also be loaded into the computer 114 and could bevisible and shown in real time on monitor 106 as the operator is placingit in the screw heads 255.

In an alternative procedure, one or more plates and/or one or more wiresmay be inserted instead of one or more rods 360.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention and inconstruction of this surgical navigation system without departing fromthe scope or spirit of the invention. Other embodiments of the inventionwill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein. It isintended that the specification and examples be considered as exemplaryonly.

What is claimed is:
 1. An apparatus for facilitating percutaneousplacement of surgical instruments into the spine, adapted for use with asurgical navigation system employing an energy-detecting array incommunication with a surgical navigation computer to track positions ofinstruments in three dimensional space relative to a known referencepoint, said apparatus comprising: a connector adapted to be rigidlyattached to a portion of the spine; at least one central post connectedto said connector; a position identification structure rigidly andremovably connected to said central post at a predetermined position onsaid central post and adapted to be reconnected at the same saidpredetermined position, said identification structure being furtheradapted to allow a patient to be scanned with the structure connected tothe central post, said structure including an assembly for communicatingpositioning information with respect to said assembly to the energydetecting array and surgical navigation computer; and a connectorassembly for said reconnecting of said structure substantially to saidpredetermined position on said central post.
 2. The apparatus of claim1, wherein the connector is a clamp having teeth adapted for biting intoa spinous process.
 3. The apparatus of claim 1, wherein the connectorincludes an elongated fixture with a central axis and a threaded endadapted to be inserted into the spinous process and a substantiallyrigid wire connected to the fixture with the central axis of the wireadapted to be implanted into the spinous process at an angle toelongated fixture to prevent the fixture from rotating.
 4. The apparatusof claim 1, wherein said assembly for communication positioninginformation is a substantially H-shaped frame.
 5. The apparatus of claim1, wherein said assembly for communicating positioning information is asubstantially W-shaped frame.
 6. The apparatus of claim 1, wherein saidassembly for communicating positioning information is a substantiallyU-shaped frame.
 7. The apparatus of claim 1, wherein said assembly forcommunicating positioning information is a substantially X-shaped frame.8. The apparatus of claim 1, wherein said assembly for communicatingpositioning information comprises: a fiducial array for registering thelocation of a spinal element with rigidly connected fiducials; and areference arc for signaling the position of a spinal element, said arcfurther comprising rigidly connected emitters.
 9. The apparatus of claim1, wherein said reference point is on the spine.
 10. A method formonitoring the location of an instrument, surgical implant and variousportions of the body, to be operated on, using a surgical navigationsystem with a surgical navigation computer and a digitizer array formonitoring the location of instruments in three-dimensional spacerelative to a known reference point, said method comprising the stepsof: attaching a fixture having a central post to a portion of the spine;removably attaching an identification structure including a fiducialarray and a reference arc to said central post; providing a scannedthree-dimensional image of a patient including said fiducial arrayrigidly attached to said central post of said fixture, said fixturebeing rigidly attached to the patient to identify the position of saidfixture and said fiducial array on the scanned image; using animage-guided system, by touching an image guided surgical pointer to oneor more fiducials on the fiducial array to register the location of aspinal element fixed to said array; and emitting a signal from saidreference arc to indicate changes in position of the spinal elementduring a surgical procedure.
 11. The method of claim 10, furthercomprising: performing a surgical procedure percutaneously on a patientusing an instrument and implant locatable relative to the spinal elementand said structure in known positions identified in the surgicalnavigation system.
 12. The method of claim 10, further comprising:inserting a threaded fixture having a substantially rigid wire into aspinal element; and touching an image guided pointer to said threadedfixture and wire to positively register the location of said fixture andwire in a surgical navigation computer.
 13. The method of claim 10,further comprising: implanting imageable devices into spinal elements toidentify the location of the spinal elements in the surgical navigationcomputer.
 14. The method of claim 10, further comprising: implantingimageable devices into a plurality of spinal elements; and manipulatingthe patient's spine by viewing the location of the implanted devices, ascommunicated to the surgical navigation computer by touching aninstrument with a tracking emitter to said implanted imageable devicesto align the actual position of the spinal elements with the previouslyscanned image.
 15. The method of claim 10 further comprising:percutaneously implanting screws into spinal elements; and locating theposition of said screws using image guided surgical navigationtechniques.
 16. The method of claim 15 further comprising: manipulatingthe orientation of the screw heads percutaneously using ahead-positioning probe for communicating location containing an emitter,said probe communicating to the surgical navigation computer theorientation of the screw heads; and using a head positioning tool formanipulating implants having an end portion that mates with the heads ofthe screws and rotating the screws to receive a connecting implant. 17.The method of claim 16 further comprising: tracking the location andposition of the connecting implant by means of an instrument affixed tothe implant having emitters capable of communicating orientation andlocation to the surgical navigation computer.
 18. A system for use inperforming the percutaneous placement of surgical implants andinstruments into the spine using image guided surgery and a surgicalnavigation computer and energy detecting array, said system comprising:means for attaching a fixture to a portion of the spine; means forcommunicating position information to the surgical navigation computerand energy detecting array said means rigidly and removably connected tosaid means for attaching a fixture; means for providing locationinformation of said spinal portion to the surgical navigation systemadapted to be connected to spinal elements; means for indicatingscrew-head position said means electrically connected to the surgicalnavigation system and adapted to mate with the head of a screw implantedin one or more of said spinal elements.
 19. The system of claim 18further comprising: an elongated implant adapted to be inserted intosaid implanted screws; means for indicating the position of saidelongated implant electrically connected to the surgical navigationsystem and adapted to mate with the elongated implant.
 20. The system ofclaim 18, wherein said implanted screws have heads and the elongatedimplant is a rod adapted to be guided through holes in said implantedscrew heads.
 21. A method of registering a physical space definedrelative to a subject to an image space of the subject, comprising:connecting an attaching device to the subject; connecting at least oneof a fiducial portion or a reference portion to the connected attachingdevice with a connector in a geometric orientation and location;acquiring image data of the subject and the connected at least onefiducial portion or reference portion that is connected to the subjectin the geometric orientation and location; removing the connected atleast one fiducial portion or reference portion from the connected atleast one clamp or screw after acquiring the image data; and registeringthe physical space of the subject to the image space of the acquiredimage data, including: reattaching at least one of the fiducial portionor the reference portion to the connected attaching device in thegeometric orientation and location as during the acquiring the imagedata, and determining a location of a registration portion of theconnected at least one fiducial portion or reference portion.
 22. Themethod of claim 21, further comprising: attaching the reference portionto the connected attaching device after acquiring the image data of thesubject.
 23. The method of claim 21, wherein determining the location ofthe registration portion of the fiducial portion includes determining alocation of at least one divot on the fiducial portion.
 24. The methodof claim 23, further comprising: folding the fiducial portion to reducea volume encompassed by the fiducial portion.
 25. The method of claim23, further comprising: removing the fiducial portion subsequent to theregistering the subject space to the image space and maintainingregistration of the subject space to the image space with the attachedreference portion.
 26. The method of claim 23, wherein determining alocation of at least one divot on the fiducial portion includes trackingan instrument to touch the at least one divot.
 27. The method of claim21, wherein connecting the attaching device to the subject includesfixing a clamp to the subject by moving a first arm and a second armtowards one another to compress a structure of the subject between thefirst arm and the second arm to hold the clamp relative to thestructure.
 28. A method of registering a physical space defined relativeto a subject to an image space of the subject, comprising: connecting adevice to the subject; connecting at least a portion of asuper-structure to the connected device with a connector; acquiringimage data of the subject and the connected at least a portion of thesuper-structure connected to the device that is connected to thesubject; removing the connected at least a portion of thesuper-structure from the connected device after acquiring the imagedata; and registering the physical space of the subject to the imagespace of the acquired image data, including: re-connecting the at leastthe portion of the super-structure to the connected device in a samegeometric orientation and location as during the acquiring the imagedata, and determining a location of a registration portion of there-connected at least a portion of the super-structure.
 29. The methodof claim 28, wherein connecting the device to the subject includesfixing at least one of a clamp or a screw to a structure of the subject.30. The method of claim 28, wherein connecting at least the portion ofthe super-structure to the connected device includes connecting at leastone of a fiducial portion or a reference arc to the fixed device with aconnector to the device.
 31. The method of claim 28, wherein connectingthe device to the subject includes fixing the device to a structure ofthe subject.
 32. The method of claim 31, wherein connecting at least theportion of the super-structure to the device includes connecting areference portion to the connected device after acquiring the image dataof the subject.
 33. The method of claim 28, wherein determining thelocation of the registration portion of the re-connected at least aportion of the super-structure includes determining a location of aplurality of divots on the at least a portion of the super-structure.34. The method of claim 33, wherein re-connecting the at least theportion of the super-structure includes re-connecting at least afiducial portion that defines the plurality of divots.
 35. The method ofclaim 34, further comprising: folding the fiducial portion to reduce avolume encompassed by the fiducial portion.
 36. The method of claim 34,further comprising: removing the fiducial portion subsequent to theregistering the physical space to the image space and maintainingregistration of the physical space to the image space via there-connected at least a portion of the super-structure.
 37. The methodof claim 36, wherein re-connecting the at least the portion of thesuper-structure includes connecting at least a reference portion;wherein maintaining registration of the physical space to the imagespace includes tracking the connected reference portion.
 38. The methodof claim 28, wherein connecting the device to the subject includesconnecting a clamp to a structure of the subject by at least moving afirst arm towards a second arm to compress the structure between thefirst arm and the second arm to hold the clamp relative to thestructure.
 39. A system for registering a physical space definedrelative to a subject to an image space of the subject, comprising: adevice operable to be connected to the subject; and at least one of areference portion operable to be detachably connected to the device or afiducial portion operable to be detachably connected to the device;wherein the reference portion is operable to determine a location of thesubject and the fiducial portion is operable to be registered relativeto an image of the subject.
 40. The system of claim 39, furthercomprising: a member extending and detachable from the device.
 41. Thesystem of claim 40, wherein the device includes a screw operable to bedriven into the subject; wherein the member is detachable from thescrew.
 42. The system of claim 40, wherein the device includes a clampoperable to compress a structure of the subject between a first arm anda second arm; wherein the member is detachable from the clamp.
 43. Theapparatus of claim 40, further comprising: a connector to interconnectthe at least one of the reference portion or the fiducial portion to themember; wherein the member extends from a first end to a second end,wherein one of the first end or the second end of the member is operableto be connected to the device; wherein the connector is connected nearthe second end; wherein the connector is operable to interconnect thereference portion and the member.
 44. The apparatus of claim 43, whereinthe connector includes a shaped interface such that the referenceportion and the member can be separated and placed back in the samegeometric orientation and location.
 45. The apparatus of claim 39,wherein the fiducial portion includes a plurality of divots operable tobe registered to increase accuracy when compared to a singleregistration divot.